The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
An internal combustion engine includes intake valves that are selectively opened to draw air into cylinders of the engine. Two-step valve lifters may be used to control opening and closing of the intake valves. The two-step valve lifters are selectively operable between a low-lift state and a high-lift state. When the valve lifters are in the high-lift state, the intake valves allow for greater displacement, increasing the amount of air and fuel taken into the engine and increasing engine torque. When lower engine torque is desired, the valve lifters may be switched to a low-lift state to reduce displacement of the intake valves, thereby reducing engine pumping losses.